1. Field of the Invention
The present invention relates generally to a mobile communication terminal, and in particular, to an apparatus and method the technology for time setting in a mobile communication terminal.
2. Description of the Related Art
Conventionally, mobile communication terminals based on a synchronous system as in a Code Division Multiple Access (CDMA) system receive time information from base stations in which they have been registered and then synchronize their time information, such that the time information is synchronized to a local time of an associated region at any time. However, unlike the synchronous system some mobile communication networks based on an asynchronous system do not provide time and date information (hereinafter, time information) in a region where a mobile communication terminal is currently located. When the mobile communication terminals using the asynchronous system (hereinafter, mobile communication terminals) move to a region of a different time zone, the users are not provided the correct time information of the current region. Thus, the users of the mobile communication terminals must manually correct internal times according to a time zone of an associated region.
There is a problem in that the users must manually perform a time synchronization process. Furthermore, there is another problem in that the manually performed time synchronization process can be incorrect, for instance when a reference clock is incorrect or the users are unfamiliar with a time information setting process.
Various methods have been provided for addressing these problems. A typical method receives a Short Message Service (SMS) message including time information from a Base Station (BS) to update internal time information of the mobile communication terminal, or updates internal time information of the mobile communication terminal according to location information received from the base station.
In the method using the SMS message, when the mobile communication terminal of the user moves to a region of a different time zone, the BS of the region in which the terminal is currently located automatically detects the movement to the different time zone and either transmits time information according to a time zone of the current region or provides the mobile communication terminal with time information in response to a request of the terminal. In another time synchronization method, the mobile communication terminal is provided with a time information Database (DB) containing time offset information relative to a time zone of each region. When moving to a region of a different time zone, the mobile communication terminal receives location information from the base station in the current region, retrieves time offset information relative to the received location information from the time information DB, and updates time information therein.
The method using the SMS message significantly relies on a mobile communication network. In order to fully utilize this method, the mobile communication network must be provided with additional functions such as a function for detecting that a particular mobile communication terminal enters a region of a different time zone when a BS transmits time information through automatic detection and a loop back function for providing time information relative to a time zone of the current region as a response to a request of the mobile communication terminal, as well as additional structures for performing the additional functions.
In the method using the SMS message, the SMS message is not exchanged in real time, and therefore, a predetermined time taken to completely exchange the SMS message corresponds to delay. Thus, there is a decrease in accuracy of newly set time information.
Alternatively, whether the time information of the mobile communication terminal is updated after the time information of a time zone of an associated region is detected using location information provided from the base station, there is still a decrease in the accuracy of time information. This is because the time information is updated on the basis of time information output from a Real Time Clock (RTC) for generating the time information inside the mobile communication terminal. This method updates the time information of the mobile communication terminal by incrementing or decrementing a value of the time information output from the RTC according to a time zone of a region in which the terminal is currently located. In this case, when the time information output from the RTC is incorrect, the time information provided from the mobile communication terminal is also incorrect.
In the mobile communication terminal based on the asynchronous system, the user directly provides time information and therefore the RTC maintains the time information. In this case, the user is to manually input initial time information. Thus, the accuracy of time information in the mobile communication terminal depends on the user's skill level or the accuracy of the user's reference clock.